1. Field of the Invention
The present invention relates to a variable capacity rotary compressor and a refrigerant cycle system having the variable capacity rotary compressor and, more particularly, to a variable capacity rotary compressor which allows a refrigerant entering the compressor after being bypassed to vary a compression capacity of the compressor, to have same temperature and pressure as when entering the compressor at first, and to a refrigerant cycle system having the variable capacity rotary compressor.
2. Description of the Related Art
As shown in FIG. 1, a conventional variable capacity rotary compressor 10 includes a cylinder 11 in which a refrigerant is compressed, an inlet pipe 12 to deliver the refrigerant into the cylinder 11, an outlet pipe 13 to deliver the refrigerant out of the cylinder 11, a bypass hole 11a provided at a predetermined position of the cylinder 11 to bypass the refrigerant from the cylinder 11 for varying a compression capacity, and a bypass pipe 14 to connect the bypass hole 11a to the inlet pipe 12 to allow the refrigerant bypassed through the bypass hole 11a to enter the cylinder 11. In the cylinder 11 is installed a roller piston 11b to be eccentric from a center of the cylinder 11. Further, a vane 11c is installed in the cylinder 11 to partition the cylinder 11 into a high-pressure part 11d and a low-pressure part 11e. The variable capacity rotary compressor also has a control unit to control a flow of the refrigerant which flows through the bypass pipe 14. In this case, the control unit includes a check valve 11f, a connection pipe 15, and a three-way valve 16. The check valve 11f functions to open or close the bypass hole 11a. The connection pipe 15 connects the outlet pipe 13 to the bypass pipe 14. Further, the three-way valve 16 is provided at a junction between the bypass pipe 14 and the connection pipe 15.
The bypass pipe 14 is divided into a first pipe portion 14a and a second pipe portion 14b by the three-way valve 16. The first pipe portion 14a is provided between the bypass hole 11a and the three-way valve 16, while the second pipe portion 14b is provided between the three-way valve 16 and the inlet pipe 12. The three-way valve 16 is controlled to allow the first pipe portion 14a to communicate with the second pipe portion 14b or the connection pipe 15.
In the conventional variable capacity rotary compressor 10, the compression capacity is varied by the three-way valve 16. When the three-way valve 16 is controlled to allow the first pipe portion 14a to communicate with the connection pipe 15, a pressure of the outlet pipe 13 acts on an outside of the check valve 11f, and an internal pressure of the cylinder 11 which is lower than the pressure of the outlet pipe 13, acts on an inside of the check valve 11f, thus dosing the check valve 11f. In this case, the refrigerant is not bypassed and thereby a large capacity compression mode is executed.
When it is required to execute a small capacity compression mode, the three-way valve 16 is controlled to allow the first pipe portion 14a to communicate with the second pipe portion 14b. At this time, a pressure of the inlet pipe 12 acts on the outside of the check valve 11f, and the internal pressure of the cylinder 11, that is, a pressure of either the high-pressure part 11d or the low-pressure part 11e of the cylinder 11, acts on the inside of the check valve 11f Since the pressure of the high-pressure part 11d is higher than the pressure of the inlet pipe 12, a higher pressure acts on the inside of the check valve 11f in comparison with the outside of the check valve 11f, thus opening the check valve 11f. Therefore, while the pressure of the high-pressure part 11d acts on the inside of the check valve 11f, the refrigerant is bypassed through the check valve 11f. In this case, the variable capacity rotary compressor 10 is operated in the small capacity compression mode.
As described above, when the variable capacity rotary compressor 10 is operated in the small capacity compression mode, the refrigerant is bypassed through the bypass pipe 14, and then the bypassed refrigerant enters the cylinder 11 through the inlet pipe 12. However, since the refrigerant bypassed from the cylinder 11 is compressed slightly, the bypassed refrigerant has temperature and pressure which are higher than those of the refrigerant when entering the cylinder 11 at first. As such, when the refrigerant having high temperature and pressure enters the cylinder 11, a mass flow is reduced, due to an increase in a specific volume of the bypassed refrigerant, thus reducing the operational efficiency of a refrigeration cycle. Further, due to an increase in a suction pressure of the compressor 10, power consumption of the compressor 10 is undesirably increased.